Method of measuring toe of vehicle wheels with enlarged scale and apparatus therefor

ABSTRACT

In measuring the toe of the front wheels of a vehicle, a projector is mounted on each wheel and aimed at a background unit in front of the vehicle. Two adjustable scales on the background unit are set so that a reference image projected from each projector hits the zero line of the scale for that wheel when the wheel is normal to the background unit. To determine the toe, the wheels are turned until one of the wheels is normal to the panel. The reference image is projected from the projector on the other wheel to a mirror on the background unit, and is reflected back to a mirror on the projector, from which it is reflected back to the adjustable scale for that wheel on the background unit. The reading on the scale, which is enlarged, gives the total toe of the vehicle wheels.

United States Patent [72] Inventor James W. Baker East Lansing, Mich.

[21] AppLNo. 799,819

[22] Filed Feb. 17,1969

[45] Patented Apr. 20, 1971 [73] Assignee FMC Corporation SanJose,Ca1if.

[54} METHOD OF MEASURING TOE OF VEHICLE WHEELS WITH ENLARGED SCALE ANDAPPARATUS THEREFOR 10 Claims, 5 Drawing Figs.

[52] U.S.CI 356/155,

[51] 1nt.CI ..G0lbI1/26 [50] FieldoiSearch 356/154,

[56] References Cited UNITED STATES PATENTS 2,150,398 3/1939 Paulson356/154 2,292,969 8/1942 Peters... 356/155 2,670,660 3/1954 Miller....350/285 2,739,504 3/1956 Egelsen 356/154 2,765,701 10/1956 Carrigan....356/155 3,159,916 12/1964 Hunter 356/155 3,363,504 1/1968 Lill 356/155Primary Examiner-Ronald L. Wibert Assistant Examiner-J. RothenbergAn0rneysF. W. Anderson and C. E. Tripp ABSTRACT: In measuring the toe ofthe front wheels of a vehicle, a projector is mounted on each wheel andaimed at a background unit in front of the vehicle. Two adjustablescales on the background unit are set so that a reference imageprojected from each projector hits the zero line of the scale for thatwheel when the wheel is normal to the background unit. To determine thetoe, the wheels are turned until one of the wheels is normal to thepanel. The reference image is projected from the projector on the otherwheel to a mirror on the background unit, and is reflected back to amirror on the projector, from which it is reflected back to theadjustable scale for that wheel on the background unit. The reading onthe scale, which is enlarged, gives the total toe of the vehicle wheels.

PATENTED-APRZOIQYI 3575.514

sum 1 UF 2 ATTORNEYS PATENTED APR20 I971 sum 2 or 2 T1E E 4 F'IE- Elll/IIETIIIOID OIF ASURING TOE OF VEHICLE WHEELS WITllll IENLARGEID SCALEAND APPARATUS THEREFOR BACKGROUND OF THE INVENTION In the alignment ofvehicle wheels, it is desirable to make the scales from whichmeasurements are read aslarge as possible to-insure accurate reading andprecise adjustment. A large scale, however, requires a large movement ofa reference mark, such as a projected image, as the alignment or adjustment of the wheels are changed. A large movement of the reference image,for a given adjustment of change of alignment of the wheel, requires along path of travel for the projected image from the wheel to the scale.However, placing the scale a long distance in front of the vehicle toprovide a long path of travel for the projected image makes the enlargedscale difficult to read because of the remoteness of the scale from thevehicle where the operator is adjusting or aligning the wheels.

SUMMARY OF THE INVENTION In the present invention, there is provided amethod of measuring toe on an enlarged scale, and apparatus therefor, in

which the scale is not remote from the vehicle. Instead, the scale is anormal distance (say 6 feet) from the front wheels of a vehicle, but thescale is five times as large as a normal scale positioned only 6 feetfrom the vehicle wheels.

The method and apparatus of the present invention is illustrated inconjunction with toe measurement. In the preferred embodiment of theinvention, a projector is mounted on each front .wheel of the vehicle. Abackground unit which carries an enlarged scale is mounted a convenientdistance (say 6 feet) in front of the vehicle. A mirror is mountedadjacent the scale, and a mirror is mounted on the front of theprojector. A reference mark, or image, is projected from the projectoralong a path determined by the alignment of the wheel on which it ismounted. The projected reference mark is reflected from the mirroradjacent the scale back to the projector. The mark is then projectedfrom the projector mirror back to the scale.

The scale is adjustably movable on the background unit so that it can bepositioned with the zero mark at the point which would coincide with theprojected reference mark if the wheel on which the projector castingthat mark were perpendicular to the background unit bearing the scale(or perpendicular to a reference plane generally parallel to andextending through the background unit). During toe measurement, however,the opposite front wheel is set perpendicular to the reference plane sothat the wheel carrying the projector which casts the reference mark isat an angle (say 0 degrees) to a plane perpendicular to the referenceplane.

Assume that a reference mark projected a distance of 6 feet (fromprojector to scale) at an angle 0 from a line perpendicular to a scalehaving a zero mark lying on said perpendicular line, would fall adistance d on the scale from said zero mark. The reference markaccording to the present invention, however, will fall on the scale adistance 5d from the zero mark, although the scale is only 6 feet fromthe vehicle. This is because the reference mark is projected fromprojector to a mirror on the background unit to projector to scale,total distance of IS feet. Thus, not only is the scale easily readable(since it is only 6 feet away) but, more importantly, more accuratereadings and adjustments can be made because of the long path (18 feet)of the projected image.

It is therefore one object of the present invention to provide a methodof an apparatus for aligning vehicle wheels in which an enlarged scaleis used. It is another object of the present invention to provide, forwheel aligning, a large scale which is not remote from the operator.Another object of the present invention is to provide an improvedtoe-measuring method and apparatus in which a projected image travels arelatively long distance to a large scale which is positioned close tothe operator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view showing thefront wheels of a vehicle in front of a background unit for wheelalignment showing projectors on the front wheels aimed at the unit;

FIG. 2 is a plan view of the vehicle of FIG. 1 showing the projectors onthe front wheels aimed at targets on the rear wheels;

FIG. 3 is an enlarged, fragmentary front view of the background unit,taken on line 3-3 of FIG. 1;

FIG. 4 is a view taken on the line 4-4 of FIG. 3; and

FIG. 5 is a side view, taken on the line 5-5, of the apparatus of FIG.I.

DESCRIPTION OF THE PREFERRED EMBODIMENT The method. and apparatus of thepresent invention is most suitable for measuring the toe of vehiclewheels. Toe can be defined as the difference in distance between theextreme front (distance A) and the extreme rear (distance B) of thetires at the height of the center of the wheels (see FIG. 1). There isshown in FIG. I the front wheels I0, 11 of a vehicle positioned in frontof a background unit I2 which lies in a reference plane 13. A referenceline 14 extending between the centers of the front wheels 10, I1 isparallel to the plane 13.

As shown best in FIGS. 3 and 4, the background unit 12 has a frame 16which supports a panel I7. A shadow box 18,

which is mounted on the background unit in front of each front vehiclewheel, has a clip I9 mounted over the frame, and the clip has a tab 20attached to each end thereof. The shadow box 18 has no front face, andthe panel 17 has an opening 21 in front of the shadow box to permit aprojected image of reference indicia to be cast into the shadow box. Aplate 22, having a toe scale marked thereon, is mounted in the back ofthe shadow box. A mirror 23 for each vehicle wheel is mounted in thebackground unit on a mirror bar 24 supported at each end by the sides ofthe frame I6. The two mirrors lie in reference plane 13, one in front ofeach of the vehicle wheels 10, II. The mirrors lie below the shadowboxes and behind openings 25 in the panel 17.

A projector 30 is mounted on each wheel. The projector has a lamp 31therein, and a condensing lens 32 is positioned in front of the lamp. Apointer 33 is mounted between the condensing lens 32 and a focusing lens34 for projection of the image of the pointer along a path 35A from theprojector to the background unit parallel to the plane of the wheel. Amirror 36 is mounted on the front of the projector facing the panel. Themirror is positioned on the projector so that an imaginary line M nonnalto the mirror surface is parallel to the path 35A of an image projectedfrom the projector.

For purposes of illustration, assume that the plane C of the left wheelII) of the vehicle is normal to the reference plane 13 and that theplane D of the right in is turned in (at the front) at an angle 0 from areference plane E which is normal to the reference plane I3. A referenceline F from the projector of wheel 11 is perpendicular to the referenceline 14 (which is parallel to the plane 13) and strikes the plane 13 atpoint G. The image of pointer 33, which travels the first leg betweenthe projector and plane 13 along the path 35A at an angle 0 with line F,strikes the plane I3 (or, more specifically, the mirror 23 thereof) atpoint H. The distance d between points G and H represents the size ofthe scale reading if the image of pointer 33 were projected on a scalewith only one leg of travel between the projector and the backgroundunit.

However, the image of pointer 33 strikes mirror 23 and is reflected backalong a second leg on path 353 to the mirror 36 on the projector. Itshould be noted that leg 35A is at an angle 0 to an imaginary line Kperpendicular to the plane I3 at H. Similarly, leg 35B is at an angle 6to line K, but on the other side thereof as the leg 35A, so the angularspan between legs 35A and 35B is 26.

The image of pointer 33 strikes the mirror 36 at the projector and isreflected back to the panel to point P on a third leg defined by path35C. The leg 35B is at an angle 0 with a reference line L which extendsfrom mirror 36 parallel to lines F and K (that is, normal to plane 13and line 14). A reference line M from mirror 36, which is normal to themirror 36, is at an angle 6 to line L since the mirror is tilted at anangle to line 14. The leg 35C, which is spaced from leg 358 at twice theangle it is spaced from line M, is at an angle of 46 from leg 358. Sincethe image would be at H, a distance d from point G, when projected at anangle 0 from normal line F, and would be at point P, a distance 4d frompoint H when reflected from point H to point P, it can be seen that athree leg pass of the image of pointer 33 will place the'final image atP on plane 13, a distance 5d from point G. This permits use of a scalefive times the size of a scale which could be used if the final image tobe read was projected at H.

It is important that the scale at the panel be set so that the zero markon the scale is positioned at point 0 (to indicate a zero toe) if theplane D of the wheel 11 is normal to the line 14 and plane 13. For thisreason, the shadow box 18, in which the scale 22 is mounted, is slidablealong the panel by pushing or pulling on the tabs 20.

In order to set the box 18 and scale 22 in the right position. theprojectors are aimed at target scales 40 on the rear wheels. as shown inFIG. 2, and the front wheels are centered by turning the wheels untilthe images projected from the two projectors give equal readings on thetwo targets 40. The projectors are then aimed at the two mirrors in thepanel, as shown in FIG. 1, and the bar 24 on which the mirrors aremounted is shifted horizontally, about one end or the other, until thepointer images reflected onto the projector mirror give equal readingson scales marked on the two projector mirrors. This positions the mirrorbar 24 parallel to reference line 14.

The wheels are then turned until the image projected from the projectoron the right wheel is reflected back to the zero mark on a scale on theprojector mirror. With the wheel thus positioned, the right-hand shadowbox 18 is set so that the projected pointer image falls on zero of thescale (which will be at point G of FlG. t). Thereafter, the wheels areturned until the projected pointer image of the projector of wheel isreflected back on the zero mark of the scale of that projector mirror toindicate that the wheel is normal to line 14. At that time, the totaltoe of the wheels can be read from the image projected by the projectorof wheel H on the righthand scale 22.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

lclaim:

l. The method of indicating toe alignment of vehicle wheels comprisingthe steps of projecting an image from a front wheel of the vehicleforwardly toward a screen, reflecting said image from said screen backtoward the wheel, and reflecting said image from the wheel back towardsaid screen, said image and said screen presenting a scale reading toindicate the amount of toe to an operator underneath the vehicle.

2. The method of indicating the toe of vehicle wheels comprising thesteps of projecting an image forwardly toward a background unit from aprojector mounted on a front wheel of the vehicle, reflecting said imageback toward said wheel from a mirror mounted at the background unit, andreflecting said image back toward said background unit from a mirror atsaid projector, said image on said background unit presenting a scalereading to indicate the amount of toe to an operator underneath thevehicle.

3. The method of indicating the toe of vehicle front wheels comprisingthe steps of placing one front wheel and then the other front wheelperpendicular to a reference plane in front of the vehicle, projectingan image forwardly from each front wheel parallel to the wheels,adjusting a scale for each wheel in the reference plane to apredetermined position when each wheel is perpendicular to the referenceplane, setting one wheel erpendicular to the reference plane, reflectingthe image rom the other wheel from a mirror at the reference plane backto the wheel, and reflecting said image from said other wheel back tothe scale for that wheel at the reference plane to indicate the amountof toe between the wheels to an operator underneath the vehicle.

4. The method of indicating the toe of vehicle front wheels comprisingthe steps of placing one front wheel and then the other front wheelperpendicular to a reference plane, projecting a reference markforwardly along a path parallel to each wheel from a projector on therespective wheels, adjusting a movable scale for each wheel at thereference plane to set the zero mark of the scale for each wheel at thereference mark projected from that wheel when the respective wheels areperpendicular to the reference plane, setting one wheel perpendicular tothe reference plane, reflecting the reference mark from the projector onthe other wheel from a mirror at the reference plane back to theprojector from which it was projected, reflecting the reference markfrom a mirror on the projector back to the scale at the reference planeto give an enlarged toe reading visible to an operator underneath thecar.

5. Apparatus for indicating the toe of vehicle front wheels comprising aprojector mounted on a front wheel to project a reference markforwardly, a first mirror in front of the vehicle positioned to reflectthe reference mark back to the projector, a second mirror at theprojector to reflect the reference mark back toward the first mirror,and a marked surface at the first mirror to receive the projectedreference mark, said reference mark and said marked surface giving ascale reading indicating the extent of toe to an operator underneath thevehicle.

6. The apparatus of claim 5 in which said marked surface is movable forsetting.

7. Apparatus for indicating the toe of vehicle front wheels comprising aprojector mounted on each front wheel to project a reference markforwardly, a first mirror in front of each projector, said first mirrorspositioned to reflect the reference marks back to the projector fromwhich they were projected, a second mirror at each projector to reflectthe reference marks back toward the respective first mirrors, and anadjustable marked surface adjacent each of said first mirrors to receivethe projected reference mark, said reference mark on said marked surfacegiving a scale reading to an operator underneath the car.

8. Apparatus for measuring the toe of vehicle front wheels comprising aprojector mounted on one of the wheels to project a reference markforwardly, a background unit mounted in front of the projector, a firstmirror mounted in the background unit to reflect the reference mark backto the projector, a second mirror mounted on the projector to reflectthe reference mark back toward the first mirror, and a marked surface atthe background unit to receive the projected reference mark saidreference mark on said marked surface giving a scale reading indicatingthe extent of toe to an operator underneath the vehicle.

9. The apparatus of claim 8 in which said marked surface is adjustablymovable in the background unit.

10. Apparatus for measuring the toe of vehicle front wheels comprising aprojector mounted on each front wheel to project a reference markforwardly, a background unit extending in front of the projectors, afirst mirror mounted on the background unit in front of each projector,said first mirrors positionable to reflect the reference marks back tothe projector from which they were projected, a second mirror mounted oneach projector to reflect the reference marks back toward the respectivefirst mirrors, and an adjustable marked surface mounted on thebackground unit adjacent each of said first mirrors to receive theprojected reference mark, said reference mark on said marked surfacegiving a scale reading to an operator underneath the car.

1. The method of indicating toe alignment of vehicle wheels comprisingthe steps of projecting an image from a front wheel of the vehicleforwardly toward a screen, reflecting said image from said screen backtoward the wheel, and reflecting said image from the wheel back towardsaid screen, said image and said screen presenting a scale reading toindicate the amount of toe to an operator underneath the vehicle.
 2. Themethod of indicating the toe of vehicle wheels comprising the steps ofprojecting an image forwardly toward a background unit from a projectormounted on a front wheel of the vehicle, reflecting said image backtoward said wheel from a mirror mounted at the background unit, andreflecting said image back toward said background unit from a mirror atsaid projector, said image on said background unit presenting a scalereading to indicate the amount of toe to an operator underneath thevehicle.
 3. The method of indicating the toe of vehicle front wheelscomprising the steps of placing one front wheel and then the other frontwheel perpendicular to a reference plane in front of the vehicle,projecting an image forwardly from each front wheel parallel to thewheels, adjusting a scale for each wheel in the reference plane to apredetermined position when each wheel is perpendicular to the referenceplane, setting one wheel perpendicular to the reference plane,reflecting the image from the other wheel from a mirror at the referenceplane back to the wheel, and reflecting said image from said other wheelback to the scale for that wheel at the reference plane to indicate theamount of toe between the wheels to an operator underneath the vehicle.4. The method of indicating the toe of vehicle front wheels comprisingthe steps of placing one front wheel and then the other front wheelperpendicular to a reference plane, projecting a reference markforwardly along a path parallel to each wheel from a projector on therespective wheels, adjusting a movable scale for each wheel at thereference plane to set the zero mark of the scale for each wheel at thereference mark projected from that wheel when the respective wheels areperpendicular to the reference plane, setting one wheel perpendicular tothe reference plane, reflecting the reference mark from the projector onthe other wheel from a mirror at the reference plane back to theprojector from which it was projected, reflecting the reference markfrom a mirror on the projector back to the scale at the reference planeto give an enlarged toe reading visible to an operator underneath thecar.
 5. Apparatus for indicating the toe of vehicle front wheelscomprising a projector mounted on a front wheel to project a referencemark forwardly, a first mirror in front of the vehicle positioned toreflect the reference mark back to the projector, a second mirror at theprojector to reflect the reference mark back toward the first mirror,and a marked surface at the first mirror to receive the projectedreference mark, said reference mark and said marked surface giving ascale reading indicating the extent of toe to an operator underneath thevehicle.
 6. The apparatus of claim 5 in which said marked surface ismovable for setting.
 7. Apparatus for indicating the toe of vehiclefront wheels comprising a prOjector mounted on each front wheel toproject a reference mark forwardly, a first mirror in front of eachprojector, said first mirrors positioned to reflect the reference marksback to the projector from which they were projected, a second mirror ateach projector to reflect the reference marks back toward the respectivefirst mirrors, and an adjustable marked surface adjacent each of saidfirst mirrors to receive the projected reference mark, said referencemark on said marked surface giving a scale reading to an operatorunderneath the car.
 8. Apparatus for measuring the toe of vehicle frontwheels comprising a projector mounted on one of the wheels to project areference mark forwardly, a background unit mounted in front of theprojector, a first mirror mounted in the background unit to reflect thereference mark back to the projector, a second mirror mounted on theprojector to reflect the reference mark back toward the first mirror,and a marked surface at the background unit to receive the projectedreference mark said reference mark on said marked surface giving a scalereading indicating the extent of toe to an operator underneath thevehicle.
 9. The apparatus of claim 8 in which said marked surface isadjustably movable in the background unit.
 10. Apparatus for measuringthe toe of vehicle front wheels comprising a projector mounted on eachfront wheel to project a reference mark forwardly, a background unitextending in front of the projectors, a first mirror mounted on thebackground unit in front of each projector, said first mirrorspositionable to reflect the reference marks back to the projector fromwhich they were projected, a second mirror mounted on each projector toreflect the reference marks back toward the respective first mirrors,and an adjustable marked surface mounted on the background unit adjacenteach of said first mirrors to receive the projected reference mark, saidreference mark on said marked surface giving a scale reading to anoperator underneath the car.